The invention pertains to a method for removing coumafos (O,Oxe2x80x2-diethyl-Oxe2x80x3-(3-chloro-4-methyl-7-coumarinyl)thiophosphate) from beeswax by adsorption onto activated charcoal followed by pressure filtration.
The mite Varroa jacobsoni causes the parasitic disease of honeybees known as varroatosis. The mite parasitizes the adult bees and their brood phases. After a latency period of several years, during which no clinical symptoms are observed, the colonies collapse within a short time. Early diagnosis is of decisive importance for successful therapy. Perizin(copyright) was developed by Bayer AG together with the Tierhygienisches Institut Freiburg [Department of Animal Hygiene Freiburg] for the diagnosis and therapy of varroatosis via drugs. W. Ritter, Tierhygienisches Institut Freiburg; xe2x80x9cDie Varroatose der Honigbiene, Apis mellifera, und ihre Bekxc3xa4mpfung mit Perizin(copyright)xe2x80x9d [Varroatosis of the honeybee, Apis mellifera, and its control with Perizin(copyright)], Veterinxc3xa4r-Medizinische Nachrichten, Volume 1, p. 3; G. Elwert Universitxc3xa4ts-und Verlagsbuchhandlung Marburg-Lahn; 1986.
When a mite-infested bee colony is treated with Perizin, the active ingredient coumafos is spread throughout the beehive owing to the shared metabolism during social feeding. After a certain duration of action, the active ingredient is biodegraded slowly. However, any coumafos which reaches the honeycomb wax can be enclosed and preserved therein. Being the raw material for what is known as the foundations, the basal sheets on which the bees re-establish new cells, beeswax is constantly recycled. Existing analytical results suggest that enclosed coumafos is concentrated to over 20 ppm as the wax is recycled; however, even a load of 5 ppm is considered as unacceptable. It is therefore necessary to eliminate the active ingredient at a point of the cycle between apiarist and foundation manufacturer by isolating it from the wax and disposing of it; the point of the cycle is yet to be established.
The invention pertains to a method for removing coumafos from beeswax by adsorption onto activated charcoal followed by pressure filtration, by:
a) melting the beeswax,
b) adding pulverulent activated charcoal in an amount of at least 5 g per litre of liquid wax,
c) preparing a homogeneous suspension of the mixture,
d) maintaining the suspension over a specific contact period,
e) filtering of the suspension in a pressure filter at a pressure differential at the filter medium of at least 1 bar.
In a preferred variant of the method according to the invention, the activated charcoal is brought into contact with the beeswax for at least 5 minutes prior to filtration.
The pressure differential in the filtration step is advantageously 4 to 6 bar. Owing to the low solids concentration and the comparably small particle size, the present object of the filtration can be termed a clarifying filtration. Suitable pressure filters with sufficiently large filter surfaces are, for example, disc pressure filters or candle filters. Both are closed discontinuous apparatuses for clarifying filtration with adjustable pressure differential and automated cake removal. Owing to the compact arrangement of the disc- or candle-shaped filter elements within the pressure filters, filter surfaces of over 100 m2 can be achieved. Such pressure filters are described, for example, in Ullmann""s Encyclopaedia of Industrial Chemistry, Sixth Edition, WILEY-VCH, Electronic Release 2001; Filtration, 8. Filtration Equipment, 8.3 Candle Filters and 8.5 Disk Filters.
The amount of activated charcoal is preferably 20 to 50 g per litre of melted wax. The activated charcoal employed should have as high an adsorption capacity and as good filtration properties as possible. Adsorption capacity and filtration properties of the activated charcoal are adjusted during production by the type of activation and the formulation. The activated charcoal CA 1(copyright), which is manufactured by Norit, has proved to be particularly suitable.
The contact time between activated charcoal and beeswax is preferably 30 to 90 minutes.
In an especially preferred variant of the method according to the invention, the suspension is stirred during the contact time in order to avoid settling of the activated charcoal at the container bottom. Sedimentation of the activated charcoal would lead to the separation of activated charcoal and beeswax. Owing to the probability of contact between active ingredient and adsorbent, it can be expected that a lesser amount of coumafos can be adsorbed when the activated charcoal is distributed unevenly in the suspension compared with the same amount of activated charcoal when distributed evenly.
When the method according to the invention is applied, coumafos is removed efficiently from beeswax.